The spin rate of golf balls is the end result of many variables, one of which is the distribution of the density or specific gravity within the ball. Spin rate is an important characteristic of golf balls for both skilled and recreational players. High spin rates allow more skilled players, such as PGA professionals, to maximize control of the golf ball. A high spin rate golf ball is particularly advantageous for an approach shot to the green. The ability to impart back spin to stop the ball on the green and side spin to draw or fade the ball substantially improves a player's control ability to control the golf ball. Hence, the more skilled players generally prefer a golf ball that exhibits high spin rate, in part, off scoring irons, such as the 7-iron club through the pitching wedge.
On the other hand, the recreational players who cannot intentionally control the spin of the ball generally do not prefer a high spin rate golf ball. For these players, slicing and hooking the ball are the more immediate obstacles. When a club head strikes a ball improperly, an unintentional side spin is often imparted to the ball, which can divert the ball from its intended course. Side spin also reduces the direct-line distance the ball will travel. A golf ball that spins less will help minimize the effect of a ball that is not hit squarely with the club face. Hence, recreational players typically prefer a golf ball that exhibits low spin rate.
Reallocating the density or specific gravity of the various layers of a golf ball provides an important means of controlling the spin rate. In some instances, the weight from the outer portions of the ball is redistributed toward the center to decrease the moment of inertia, thereby increasing the spin rate. In other instances, the weight from the inner portion of the ball is redistributed outward to increase the moment of inertia, thereby decreasing the spin rate.
The redistribution of weight within the golf ball is typically accomplished by adding fillers to the inner core or to an outer layer of the golf ball. Conventional fillers include the high specific gravity fillers, such as metal or metal alloy powders, metal oxide, metal searates, particulates, carbonaceous materials, or low specific gravity fillers, such as hollow spheres, microspheres or foamed particles. However, the addition of fillers may adversely interfere with the inherent resiliency of the polymers used in golf balls and thereby the coefficient of restitution of the golf balls. Hence, there remains a need in the art for a golf ball with controlled moment of inertia that has improved coefficient of restitution.